Hex maps (technically, cartograms) are useful when each area in a visualisation should have the same visual contribution. For instance, a standard geographic election map of the UK over-emphasises the winners of rural areas because they are much bigger, geographically, even though they are the same size electorally. In this case a hex map would give a better impression of the result although at the expense of accurate geography.
This site aims to bring together openly licensed hex map layouts (of UK geographies) that are available for reuse.